High voltage-high frequency vacuum switch



1966 M. c. PRITCHARD ETAL. 3,277,261

HIGH VOLTAGE-HIGH FREQUENCY VACUUM SWITCH Filed Sept. 8, 1964 F w of T4 N# fiw M 40 g CLJNYV 2 M A w W E 7 WW A an M B ated integrity of the chamber.

United States Patent 3,277,261 HIGH VOLTAGE-HIGH FREQUENCY VACUUM SWITCH Melvin C. Pritchard and Michael S. Singer, Brooklyn,

N.Y., assignors to the United States of America as represented by the Secretary of the Navy Filed Sept. 8, 1964, Ser. No. 395,102 5 Claims. (Cl. 200-144) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to switches and more particularly to vacuum switches for use at both high voltage and high frequency and having a plurality of contacts.

Heretofore vacuum wafer type switches have been limited in voltage and are a frequent source of arcingover. In addition these switches introduced relatively high stray capacitance between contacts and the dielectric shaft with its associated components in a large number of cases presented a source of gas leakage into the switch envelope. It is therefore an object of this invention to provide a reliable, simple, economical high voltage-high frequency vacuum switch exhibiting low interelectrode capacitance, low current leakage and a relatively long operating life.

Another object of this invention is to provide a vacuum switch in which the control switching element although piercing the switch envelope does not affect or increase the possibility of any gas leakage.

Other objects and advantages will appear from the following description of an example of the invention, and the novel features will be particularly pointed out in the appended claims.

In the accompanying drawings:

FIG. 1 is an elevation plan view of an embodiment made in accordance with the principle of this invention; and

FIG. 2 is a cross-section taken approximately along a line 22 of FIG. 1.

In the illustrated embodiment of the invention a closed evacuated generally cylindrical chamber formed by shell walls 11 of an electrical insulator as glass. This would correspond in most regards to the common evacuated envelope of a vacuum tube and provided with walls of sufficient thickness and strength to support both the structure itself and the internal components. In general the technique and method of fabrication of such evacuated envelopes are well known as well as any necessary metal-to-glass bonds. The chamber although generally cylindrical is somewhat enlarged at one end in order to provide the volume necessary for proper spacing and dimensioning of the switch contacts.

Disposed internally at one end of the chamber is a synchromotor 12 which may be of the standard type having three stator coil Winds S S and S and a rotor winding R. The stator and rotor leads pass through the glass walls and are sealed therein maintaining the evacu- Exteriorly of the chamber and electrically connected to the synchro motor is a synchro generator 13 or transmitter. Since physical output of a synchro is quite small and where its input is insufiicient to properly activate the motor an amplifier 14 may be disposed therebetween as well as other commonly used synchro devices employed to increase the torque output of the motor. The output shaft 15 of the synchro motor which is generally of a conducting material is coupled to an electrically insulating shaft 16 by way of a standard coupling 17. Of course in either case the coupling could be eliminated by either replacing the synchro shaft or covering it with an insulating sleeve or tubing. The insulated shaft 16 terminates in a coupling 18 which joins this shaft to a contact shaft 19 of an electrically conducting metal, as for example copper. A metallic bearing 20 houses the coupling 18 and permits the shafts to rotate freely therein while in electrical contact with the shaft 19 so as to approximate a slip ring arrangement. The bearing 20 is either joined to or as shown integral with an input terminal 21 which extends radially therefrom through the chamber wall 11 as at 22 and forms a contact element 22, exterior of the chamber. This element 22 may be of any type but preferably a high frequency high voltage connector. The contact 21 is sealed into the chamber wall 11 as is standard practice. This arrangement not only provides an external switch input, but also serves to support the switch shafts within the chamber. It should be noted that if this is not suflicient other supports extending radially from this or other bearings (not shown) may be provided and terminated or imbedded within the chamber wall 11.

The conductor shaft 19 extends, as does the entire shaft arrangement coaxially with the chamber walls 11, and terminates just short of the end wall 24 where it is supported for rotation in and by thrust type bear-ing 25 which is of a metallic conductor and has a portion 26 which extends out of the chamber to form another input terminal.

Disposed in a plane intermediate the end 24 and the bearing 20 and perpendicular to the shaft axis are a plurality of terminals (in this case six) (1-6). These terminals extend radially outward from the shaft 19 but the ends thereof are spaced therefrom and are symmetrically positioned about the shaft. These terminals are of a con ducting such as copper and have the inner ends 27 formed for intimate sliding electrical engagement with the moving switch contact 28. This contact is generally cylindrical having a central passage 29 extending lengthwise thereof encompassing the shaft 19 so as to support and rotate therewith. For this purpose the passage 29 may be of a dimension so as to provide a force fit or as illustrated the shaft includes a keyway or spline 30 with a mating recess 31 formed with the passage 29, thus insuring positive concomitant rotation of the shaft and contact, The contact 28 includes a raised portion 32 which having a movable contact member 33 extending outwardly of a recess 34 in the raised portion 32. This member 23 is generally bell shaped so that it may have limited movement into and outwardly of the opening of recess 34 and is biased in an outwardly direction by coil spring 35 to provide both positive contact and equal pressure distribution.

Summarizing the operation of' the multiple contact switch, the synchro generator 16 is zeroed or referenced with respect to axial displacement of the synchro motor 12 so that the actual physical switch contact positions correspond to indicia on the generator. Of course any form of a follower arrangement could be substituted for the synchros. As for example a stepping switch similar to that employed in switchboards, or a stepping relay circuit. This referencing includes in the end a corresponding relation between the angular physical location of the contacts l-6) and the positioning of the generator 13 so that one is indexed to the other. In other words by turning the generator shaft to the indicia 1, the shaft 19 is rotated by way of intermediate coupling shaft 16 and the motor 12 to provide an electrical contact between terminal 1 and the rotatable contact 28. It should be observed that the only elements passing through the wall 11 of the chamber 10 are stationary, non rotatable and generally small. This eliminates the problems arising in those cases where a control shaft pierces the walls and is rotatable therein.

Further by providing an electrically insulating shaft portion between the contacts, terminals and the synchro motor and a spring biased contactor both greater efficiency, voltage and lower stray capacitance are achieved. Also by providing a slip ring type of support bearing and a thrust bearing misalignment and distortion of themtatable shaft are minimized;

It will be understood that various changes in the details, materials and arrangements of parts (and steps), which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

We claim: I

'1. A multiposition high voltage vacuum switch which comprises:-

(a) a closed generally cylindrical evacuated having therein,

(b) a plurality of coaxially radially disposed internal contacts carried by the walls of said chamber and having terminal portions thereof extending outwardly of said chamber for external connection thereto,

(c) a shaft disposed coaxially with said chamber,

((1) a spring biased contactor carried by said shaft intermediate the ends thereof and rotatable therewith,

chamber (6) means for supporting said shaft within said cham (i) coupling means for coupling said shaft and said motor means,

(j) a common electrical terminal extending from with out and into said chamber and electrically connected to said contactor,

(k) whereby selective switching between said common terminal and said internal contacts may be accomplished by rotation of said shaft by said motor means and controlled by said control means.

2. The switch according to claim 1 wherein said means for support are:

(a) a thrust bearing carried by the walls of said chamber and supporting for rotation one end of said shaft,

(b) and a slip ring type bearing disposed about said shaft carried by said common terminal.

'3. The switch according to claim 2 wherein said coupling means electrically insulates said shaft from said operative means.

4. The switch according to claim 3 wherein said operative means is a synchro motor and said control means is a synchro generator and including electrical wires interconnecting said motor and generator.

5. The switch according to claim 4 wherein said shaft is of an electrically conducting material said thrust bearing is of an electrically conducting material and a portion therof extends externally of said chamber to form an auxiliary terminal.

References Cited by the Examiner UNITED STATES PATENTS 1,721,008 7/ 1929 Drahonovsky 200-26 1,831,735 11/1931 l3lum ZOO-26 X 3,079,481 2/ 1963 Jennings 200144 ROBERT K. SCI-IAEFER, Primary Examiner.

KATHLEEN H. CLAF-FY, Examiner. P. E. CRAWFORD, Assistant Examiner. 

1. A MULTIPOSITION HIGH VOLTAGE VACUUM SWITCH WHICH COMPRISES: (A) A CLOSED GENERALLY CYLINDRICAL EVACUATED CHAMBER HAVING THEREIN, (B) A PLURALITY OF COAXIALLY RADIALLY DISPOSED INTERNAL CONTACTS CARRIED BY THE WALLS OF SAID CHAMBER AND HAVING TERMINAL PORTIONS THEREOF EXTENDING OUTWARDLY OF SAID CHAMBER FOR EXTERNAL CONNECTION THERETO, (C) A SHAFT DISPOSED COAXIALLY WITH SAID CHAMBER, (D) A SPRING BIASED CONTACTOR CARRIED BY SAID SHAFT INTERMEDIATE THE ENDS THEREOF AND ROTATABLE THEREWITH, (E) MEANS FOR SUPPORTING SAID SHAFT WITHIN SAID CHAMBER (F) SAID TERMINALS BEING SPACED FROM ONE ANOTHER AND FROM SAID SHAFT FOR CONTACT WITH SAID CONTACTOR, (G) MOTOR MEANS DISPOSED WHOLLY WITHIN SAID CHAMBER FOR SELECTIVELY ROTATABLY DISPLACING SAID SHAFT, (H) CONTROL MEANS FOR SELECTIVELY ACTIVATING SAID MOTOR MEANS AND DISPOSED EXTERNALLY OF SAID CHAMBER, (I) COUPLING MEANS FOR COUPLING SAID SHAFT AND SAID MOTOR MEANS, 